等p路径十砂土本构关系的归一化特性及数值建模方法

用神经网络对土体进行建模能反映应力路径相关性、反映土的剪胀剪缩以及反映体应力、剪应力对体应变、剪应变的交互影响,因而成为一种比较理想的建模方式.能否在样本有限的情况下获得精度比较高的本构模型正是主要的研究目的.通过研究中密砂在等p路径下的三轴试验曲线,发现其应力-应变关系曲线在常规应力范围内具有归一化特性.选择合适的归一化指标对砂土三轴试验数据进行归一化,以归一化的试验数据为训练样本进行神经网络训练,得到了比较理想的砂土的神经网络本构模型.本构模型仿真值与试验值符合较好,表明所给出的建模方法是合理的.提出的建模方法可以在所有试验数据的基础上自动实现概率寻优,能有效降低噪声信号的干扰、减小试验数据的分散造成的影响.     

土的工程力学性质的颗粒流模拟

基于颗粒流理论,引入不同的颗粒接触连接本构模型,分别建立了砂土和粘性土的颗粒流模型.通过颗粒流数值模型试验,对砂土和粘性土的室内平面应变试验及其剪切带形成和发展进行了数值模拟,分别对比了不同围压下颗粒流试样与室内试验的应力应变关系曲线,基本再现了砂土和粘性土试样应力-应变关系.通过砂土和粘性土PFC试样剪切带模拟表明,当围压较小时试样内部颗粒位移量小而且分布范围较广,当围压增大时,试样内部颗粒位移量也增大,而且发生较大位移颗粒的分布范围趋于集中,同时随着围压的增大试样内部形成明显的剪切带.无论砂土还是粘性土的PFC试样,随着围压的增加剪切带的形状趋于集中,而且剪切带宽度在减小.在围压很小时,试样内形成大的破坏区域,在围压较大时出现明显的线破坏区.这些规律基本与室内试验结果相似.     

Selective Extraction and Separation of Thorium from Monazite Using N-Phenylbenzo-18-crown-6-hydroxamic Acid

A method for the liquid–liquid extraction, separation, preconcentration and trace determination of thorium with N-phenylbenzo-18-crown-6-hydroxamic acid (PBCHA) is described. Thorium is extracted from the dichloromethane solution of PBCHA at pH 4.5 which gives a colourless extract (_max 375nm, =1.5×10⁴Lmol^–1 cm^–1, linear range following Beers law 0.77–18.48µgmL^–1). The extract is directly inserted into the plasma for ICP-AES measurements of thorium. A linear calibration graph was obtained between 10 and 130ngmL^–1 of thorium. The proposed method has been applied for the separation and determination of thorium in the presence of several ions in monazite sand, rare earths, sand and sea water samples. The thorium-PBCHA complexes are very stable, having the formation constant (log ₂) 13.45 compared to lanthanum (log ₂) 2.95, cerium (log₂) 2.95 and uranium (log ₂) 3.80. Hence, thorium can easily be separated and determined in monazite sand.Received October 31, 2002; accepted April 13, 2003 Published online July 16, 2003     

Hydro-mechanical aspects of the sand production problem

This paper examines the hydro-mechanical aspect of the sand production problem and sets the basic frame of the corresponding mathematical modelling. Accordingly, piping and surface erosion effects are studied on the basis of mass balance and particle transport considerations as well as Darcy's law. The results show that surface erosion is accompanied by high changes of porosity and permeability close to the free surface. Quantities which can be measured in experiment, like the amount of produced solids or fluid discharge, can be used in an inverse way to determine the constitutive parameters of the problem.Notation dV Volume element - dV _s Volume of solids pt - dV _v Volume of voids - dV _ff Volume of fluid phase - dV _fs Volume of fluidized-particles - Volume of mixture - dM _s Mass of solids - dM _ff Mass of fluid phase - d _{M fs} Mass of fluidized-particles - Mass of mixture - s Density of solids - f Density of fluid - ff Density of fluid phase - fs Density of fluidized-particles - Density of mixture - _i ^ff Velocity of fluid - _i ^fs Velocity of fluidized-particles - _i ^s Velocity of solids - Velocity of mixture - q ^ff Volume-discharge of fluid - q ^fs Volume-discharge of fluidized-particles - Volume-discharge of mixture - m ^ff Mass-discharge of fluid - m ^fs Mass-discharge of fluidized-particles - Mass-discharge of mixture - _er Rate of mass-eroded - _dep Rate of mass-deposited - Mass generation term - dS _i Surface element - Pore-surface element - D _IJ Tensor of mechanical dispersion - x _i Location - t Time - Porosity - c Transport concentration - c _cr Critical value ofc - p Fluid-pressure - k Permeability coefficient - _k Kinematic viscosity - Spatial frequency of erosion starter points     

青海油砂矿的物理化学特性

油砂矿的物理、化学性质是其开发利用的关键因素之一 ;作者利用多种分析手段 ,揭示了青海出露油砂的特殊有机物化学组成与分布及其物理性质 ,其轻质组分含量很高 ,饱和烃含量高达近一半 ,而胶质、沥青质重组分含量低 (<38 % ) ,H和C原子比甚高 ,直链烷烃分布规整 ,主要集中在C19～C37 范围 ,物理参数处在普通重油范围内 ;该种物理、化学性质独特的出露油砂在全球为首次发现 ,是青海油砂矿特殊的地理地质环境所造成的 ,作者建议其开采宜采用钻井采油和露天开采依次进行的新组合方法     

Enthalpy of adsorption and adsorption isotherms of polyacrylamide on sea sand

The enthalpy of dilution of polyacrylamide 3530s (HPAM) solution, the enthalpy of adsorption of the polymer on sea sand, and the adsorption isotherms, were determined at 298. 15 K. The effect of NaCl on these properties were also determined. From the experimental results and certain assumptions, it was deduced that, for an adsorbedHPAM molecule, a large number of segments are in contact with the surface of the solid, some of them forming hydrogen-bonds, most of them belonging to Van der Waals interactions, which are much weaker than hydrogenbonds, and theHPAM molecules adsorbed on the surface of the solid are spread out.     

青海出露油砂沥青的烃类组成分析

利用气相色谱(GC)和气相色谱／质谱联机(GC／MS)检测了青海出露油砂沥青的烃类组成与分布。结果表明，其为陆源湖相有机质生成的原油经生物氧化降解形成的。由于所处的独特地理、地质环境，其生物氧化降解程度低，饱和烃含量甚高，分布规整，轻质组分很多，明显不同于其它地区的油砂沥青。鉴于其特殊的化学组成与分布，该油砂矿必须采用新的方式进行开采。     

排水固结法的优化设计

经过排水固结法的经济分析及软土排水固结过程中的强度分析，提出了砂井参数及加载计划（工期）的优化设计方法。     

Lipids from the sand dollar <Emphasis Type="Italic">Scaphechinus mirabilis</Emphasis>

The composition of lipids and their fatty acids in tissues of scalp, gonads, and internal organs of the sand dollar Scaphechinus mirabilis was determined using one-and two-dimensional TLC and GC-MS. Lipids of S. mirabilis scalp consisting of several neutral and phospholipids were characterized for the first time. A significant quantity of eicosapentaenoic acid (20:5) was found in scalp lipids. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 320–323, July–August, 2007.     

The physics of Aeolian sand transport

We give a synthetic overview of the state of art of the physics of sand Aeolian transport. We first present the main ideas developed by Bagnold in the middle of the last century. We then review the recent experimental and theoretical advances made in the field and emphasize that the particle flow rate does not exhibit a cubic dependence with the air friction speed, as predicted by Bagnold, but a quadratic one. Finally, we list important open issues that remain.